Add regex_match Jinja filter (#1556)

# What this PR does
Adds a new `regex_match` filter to Jinja environment.

## Which issue(s) this PR fixes
This should be useful on its own, and also helpful for
https://github.com/grafana/oncall/pull/1555.

## Checklist

- [x] Tests updated
- [x] Documentation added
- [x] `CHANGELOG.md` updated

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Added
+
+- Add `regex_match` Jinja filter ([1556](https://github.com/grafana/oncall/pull/1556))
+
 ### Changed
 
 - Allow passing `null` as a value for `escalation_chain` when creating routes via the public API ([1557](https://github.com/grafana/oncall/pull/1557))

docs/sources/alert-behavior/alert-templates/index.md

@@ -176,3 +176,4 @@ Built-in functions:
 - `iso8601_to_time` - converts time from iso8601 (`2015-02-17T18:30:20.000Z`) to datetime
 - `datetimeformat` - converts time from datetime to the given format (`%H:%M / %d-%m-%Y` by default)
 - `regex_replace` - performs a regex find and replace
+- `regex_match` - performs a regex match, returns `True` or `False`. Usage example: `{{ payload.ruleName | regex_match(".*") }}`

engine/common/jinja_templater/filters.py

@@ -30,3 +30,10 @@ def regex_replace(value, find, replace):
         return re.sub(find, replace, value)
     except (ValueError, AttributeError, TypeError):
         return None
+
+
+def regex_match(pattern, value):
+    try:
+        return bool(re.match(value, pattern))
+    except (ValueError, AttributeError, TypeError):
+        return None

engine/common/jinja_templater/jinja_template_env.py

@@ -3,7 +3,7 @@ from jinja2 import BaseLoader
 from jinja2.exceptions import SecurityError
 from jinja2.sandbox import SandboxedEnvironment
 
-from .filters import datetimeformat, iso8601_to_time, regex_replace, to_pretty_json
+from .filters import datetimeformat, iso8601_to_time, regex_match, regex_replace, to_pretty_json
 
 
 def raise_security_exception(name):
@@ -18,3 +18,4 @@ jinja_template_env.filters["tojson_pretty"] = to_pretty_json
 jinja_template_env.globals["time"] = timezone.now
 jinja_template_env.globals["range"] = lambda *args: raise_security_exception("range")
 jinja_template_env.filters["regex_replace"] = regex_replace
+jinja_template_env.filters["regex_match"] = regex_match

engine/common/tests/test_apply_jinja_template.py

@@ -14,6 +14,18 @@ def test_apply_jinja_template():
     assert payload == result
 
 
+def test_apply_jinja_template_regex_match():
+    payload = {"name": "test"}
+
+    assert apply_jinja_template("{{ payload.name | regex_match('.*') }}", payload) == "True"
+    assert apply_jinja_template("{{ payload.name | regex_match('tes') }}", payload) == "True"
+    assert apply_jinja_template("{{ payload.name | regex_match('test1') }}", payload) == "False"
+
+    # Check that exception is raised when regex is invalid
+    with pytest.raises(JinjaTemplateError):
+        apply_jinja_template("{{ payload.name | regex_match('*') }}", payload)
+
+
 def test_apply_jinja_template_bad_syntax_error():
     with pytest.raises(JinjaTemplateError):
         apply_jinja_template("{{%", payload={})